Many surfaces in the human body that are exposed to blood flow are at risk of blood component deposit formation thereon. Such deposits can include, for example, blood platelets, fibrinogen, minerals such as calcium, and the like. Deposit formation on surfaces located at areas of the body which are critical to blood transmission can be detrimental or even hazardous to the person's health. For example, deposit formation on heart valves, veins, and arteries can restrict the flow of blood therethrough and/or reduce the functionality thereof. As a result, deposit formation can lead to obstructed blood flow through at least portions of the body, which limited blood flow can have serious negative implications on the health of the person.
A common form of coagulative deposition on surfaces within the body is thrombosis. This phenomenon is a result of cumulative blood component adhesion to a surface, and can have a variety of causes. In some cases, thrombosis is believed to be caused by turbulence in the blood stream, with such turbulence causing relatively forceful impact among red blood cells that causes damage to the cells, and ultimately proneness to adhere to surfaces.
While thrombosis can and does occur around native tissue surfaces, it has been found that implanted medical devices often times act as focal points for thrombogenesis. Virtually all types of implanted medical devices bear some thrombogenic characteristics, in that the implantation of such devices typically alter to some extent the normal interaction of blood flow at the implantation site. Some medical devices, however, have been found to be particularly susceptible to thrombogenesis. Artificial heart valves are an example of such implanted medical devices that bear relatively significant thrombogenetic characteristics. While materials and design for recently developed heart valves have reduced the risk of thrombogenesis, patients receiving such artificial heart valves typically are required to maintain an anti-coagulative drug protocol for the remainder of their lives. Current anti-coagulative drug therapy is far from ideal. Each patient with an implanted heart valve not only carries a risk for valve thrombosis or systemic emboli, but also a risk of bleeding which follows anti-coagulant therapy. Thromboemboli and hemorrhage comprise the majority of complications occurring in patients with artificial heart valves.
It is therefore a principal object of the present invention to provide a method for inhibiting thrombogenesis on a surface of a body in vivo with a reduced or eliminated need for anti-coagulant medication.
It is a further object of the present invention to provide a method for inhibiting thrombogenesis on the surface of a body in vivo by delivering electropositive current to such surface.
It is a still further object of the present invention to provide a method for inhibiting blood component coagulation on a surface of an implanted medical device by delivering sub-threshold electropositive current from an electrical energy source to the surface of the implanted medical device.
It is a still further object of the present invention to inhibit blood platelet adhesion to a surface in vivo by coupling the surface to an implanted electrical energy source, wherein such electrical energy source provides an electropositive current density on the surface of between about 0.001 and about 1 mA/cm2 to the target surface.